Process of producing cyclohexylbenzene

Abstract

In a process for producing cyclohexylbenzene, benzene is contacted with hydrogen in the presence of a hydroalkylation catalyst under hydroalkylation conditions effective to form a first effluent stream comprising cyclohexylbenzene, cyclohexane, and benzene. At least a portion of the cyclohexane from the first effluent stream is then contacted with hydrogen in the presence of a dehydrogenation catalyst under dehydrogenation conditions effective to convert at least some of the cyclohexane into benzene contained in a second effluent stream. At least some of the hydrogen is supplied to the process so as to contact the dehydrogenation zone (e.g., the dehydrogenation catalyst) before contacting the hydroalkylation catalyst.

The invention claimed is: 
     
       1. A process for producing cyclohexylbenzene, the process comprising:
 (a) contacting benzene with a hydrogen-containing stream in the presence of a hydroalkylation catalyst under hydroalkylation conditions effective to form a first effluent stream comprising cyclohexylbenzene, cyclohexane, and benzene; 
 (b) contacting the first effluent stream with a make-up hydrogen stream to separate the first effluent stream into a vapor-phase stream comprising hydrogen, cyclohexane, and benzene, and a liquid-phase stream comprising cyclohexylbenzene; 
 (c) contacting at least a portion of the vapor-phase stream comprising hydrogen, cyclohexane, and benzene with a dehydrogenation catalyst in a dehydrogenation reaction zone under dehydrogenation conditions effective to convert at least a portion of the cyclohexane into benzene and produce a second effluent stream comprising benzene and a hydrogen recycle stream; and 
 (d) recycling the hydrogen recycle stream to step (a) to form at least a portion of the hydrogen-containing stream. 
 
     
     
       2. The process of  claim 1 , wherein the make-up hydrogen stream comprises at least one impurity selected from carbon monoxide and an oxygenate, and at least a portion of the impurity is removed through contact with said dehydrogenation catalyst prior to step (d). 
     
     
       3. The process of  claim 2 , wherein at least 10 wt % of the impurity is removed based on weight of the make-up hydrogen stream. 
     
     
       4. The process of  claim 2 , wherein the impurity is carbon monoxide. 
     
     
       5. The process of  claim 2 , wherein the oxygenate is an aldehyde or a ketone. 
     
     
       6. The process of claim wherein at least a portion of the make-up hydrogen stream contacts the dehydrogenation catalyst before contacting the first effluent. 
     
     
       7. The process of  claim 1 , wherein the first effluent is separated in a gas/liquid separator and at least a portion of the cyclohexylbenzene in the liquid phase is recovered. 
     
     
       8. The process of  claim 1 , wherein at least a portion of the vapor-phase stream is recycled to step (a). 
     
     
       9. The process of  claim 7 , wherein said make-up hydrogen stream is supplied in a direction countercurrent to the first effluent. 
     
     
       10. The process of  claim 1 , wherein the make-up hydrogen stream is contacted with the first effluent stream in a stripper located downstream of step (a). 
     
     
       11. The process of  claim 1 , wherein step (a) is conducted in a plurality of reaction zones connected in series and the make-up hydrogen stream is supplied at or adjacent to the outlet of the final reaction zone. 
     
     
       12. The process of  claim 1 , wherein the contacting step (a) is conducted in three series reaction zones connected in series. 
     
     
       13. The process of  claim 1 , wherein the hydroalkylation catalyst comprises at least one molecular sieve and at least one hydrogenation metal. 
     
     
       14. The process of  claim 13 , wherein the at least one molecular sieve is selected from zeolite beta, mordenite, zeolite X, zeolite Y, and a molecular sieve of the MCM-22 family. 
     
     
       15. A process for producing cyclohexylbenzene, the process comprising:
 (a) contacting benzene with hydrogen in the presence of a hydroalkylation catalyst under hydroalkylation conditions effective to form a first effluent stream comprising cyclohexylbenzene, cyclohexane, and benzene; 
 (b) contacting said first effluent stream with a make-up hydrogen stream such that said first effluent stream is a mixed gas and liquid phase stream, wherein at least a portion of the cyclohexane and benzene is in the vapor phase; and 
 (c) separating the first effluent stream into a vapor-phase stream comprising hydrogen, cyclohexane, and benzene, and a liquid-phase stream comprising cyclohexylbenzene. 
 
     
     
       16. The process of  claim 15 , wherein at least a portion of the vapor phase stream comprising hydrogen, cyclohexane, and benzene contacts a dehydrogenation catalyst under dehydrogenation conditions effective to convert at least a portion of the cyclohexane to benzene and produce a dehydrogenation effluent comprising benzene and hydrogen. 
     
     
       17. The process of  claim 16 , wherein the make-up hydrogen stream contacts said dehydrogenation catalyst before contacting said first effluent and at least a portion of the hydrogen in the dehydrogenation effluent is recycled to step (a). 
     
     
       18. The process of  claim 15 , wherein at least part of the vapor phase stream is recycled to step (a). 
     
     
       19. The process of  claim 15 , wherein the hydroalkylation catalyst comprises at least one molecular sieve and at least one hydrogenation metal. 
     
     
       20. The process of  claim 19 , wherein the at least one molecular sieve is selected from zeolite beta, mordenite, zeolite X, zeolite Y, and a molecular sieve of the MCM-22 family.